Chain jumping

[Cullin]

I agree that you should check to see if you have a stiff link, if it jumps as it goes through at the back.

 

[jimboalee]

My £5 is on :-

"The chain is too long causing the mech springs to be too relaxed."

 

[Dave5N]

A common cause.

I assumed this was a recent development, so that rules out a chain that's too long or the wrong BB.

Bent hanger does this every time. I have seen it so often I went and bought a realignment gadget.

A stiff link would prob. cause it to jump under pressure going forward as well.

 

[peanut]

A common cause.

I assumed this was a recent development, so that rules out a chain that's too long or the wrong BB.

Bent hanger does this every time. I have seen it so often I went and bought a realignment gadget.

A stiff link would prob. cause it to jump under pressure going forward as well.

do you ever read previous threads Dave I said this already .
ps can we all borrow your gadget

 

[Dave5N]

Do you?

Cos I said it firstest.

Yes you can. But you'll have to come and get it. I don't do 'Deliverance'.

 

[Halfmanhalfbike]

My £5 is on :-

"The chain is too long causing the mech springs to be too relaxed."

And the winner is.............

That's it. Shortened the chain by 1 link and the prob went way.

Thanks

Next question is how tight should a chain be anyway?

 

[Dave5N]

Put your fingers against the underside of the top run of the chain.

Turn the cranks a full 2.8 revolutions.

If the bones are not crushed, the chain is too loose.

If the fingers are severed, the chain is too tight.

You'll only get it wrong twice.

Basically, get it as tight as you can without it being stupid tight when it's on the big ring on the front (Right Hand Side) and the big cog at the back (LHS).

You don't need ever to ride this combination, but you need to know the chain will accommodate it.

Secondly, put it in the smallest two rings, Front and Back, and check it isn't flopping about. If it is, you need to adjust the rear derailleur, or more likely, a longer cage one.

Lastly, was your back-pedalling derailment problem an inherent one or a developed one?

 

[peanut]

Basically, get it as tight as you can without it being stupid tight when it's on the big ring on the front (Right Hand Side) and the big cog at the back (LHS).

Secondly, put it in the smallest two rings, Front and Back, and check it isn't flopping about. If it is, you need to adjust the rear derailleur, or more likely, a longer cage one.

suggest you read the Shimano guide and do the job properly .


Shimano chain and rear mech setup guide http://techdocs.shimano.com/media/t...RA/RD-4400/5TS0B_EN_v1_m56577569830607031.PDF

 

[Dave5N]

Still smarting?

 

[peanut]

Still smarting?

just trying to make sure the OP gets the correct advice

 

[jimboalee]

If your Dad has got a fishing spring balance, hook it onto the bottom of the derailleur cage and pull it along the line of the chain.

It should be 1kg.

 

[Halfmanhalfbike]

Lastly, was your back-pedalling derailment problem an inherent one or a developed one?

Developed by me!

I had just stripped the bike down to it's component parts and reassembled them. It was OK before I did this

Dont really mind though as the whole reason I bought the bike was to use it as a test bike to learn some maintenance

Bike came from great place called http://www.thebikestation.org.uk Great place